1. Field of the Invention
The invention relates generally to the field of metering of tv sets for the purpose of audience measurement, and more particularly to metering of those homes having both a tv set and a VCR.
2. Brief Description of the Prior Art
Audience measurement for commercially supported tv is typically determined by meters connected to the antenna inputs and the tv sets of the audience. The meters determine when and for how long a tv set is tuned to particular channels. Most meters do this by injecting a special signal into the channels one by one and monitoring the tv's tuner output for the presence of this signal.
VCR's present many complications to this traditional scheme. First they contain their own tuner's by which the input to the tv set on the VCR output channel (typically channel 2, 3 or 4) may be any one of the broadcast (cable) channels. Determining that the tv is tuned to channel 3, for example proves nothing. Second, the householder may recorded one channel while viewing another using his tv's tuner and view the recorded program later. Finally, during record or playback, he may use the VCR/TV button to pass the antenna input directly to the tv, bypassing a conventional tv meter connected to the antenna inputs.